Method of processing substrate, method of manufacturing semiconductor device, substrate processing apparatus, and recording medium

ABSTRACT

There is provided a technique that includes: forming a film containing Si, O and N or a film containing Si and O on a substrate by performing a cycle a predetermined number of times under a condition where SiCl 4  is not gas-phase decomposed, the cycle including non-simultaneously performing: (a) forming NH termination on a surface of the substrate by supplying a first reactant containing N and H to the substrate; (b) forming a SiN layer having SiCl termination formed on its surface by supplying the SiCl 4  as a precursor to the substrate to react the NH termination formed on the surface of the substrate with the SiCl 4 ; and (c) reacting the SiN layer having the SiCl termination with a second reactant containing O by supplying the second reactant to the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 17/497,570, filed on Oct. 8, 2021, which is a continuation of U.S. patent application Ser. No. 16/445,077, filed on Jun. 18, 2019, issued as U.S. patent Ser. No. 11/164,741 on Nov. 2, 2021, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-116976, filed on Jun. 20, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing a semiconductor device, a substrate processing apparatus, and a recording medium.

BACKGROUND

As an example of processes of manufacturing a semiconductor device, a process of forming a film containing silicon (Si), nitrogen (N), and oxygen (O), i.e., a silicon oxynitride film (SiON film), on a substrate is often carried out in the related art.

SUMMARY

The present disclosure provides some embodiments of a technique that improves film thickness uniformity of a SiON film or a SiO film formed on a substrate in the plane of the substrate.

According to an embodiment of the present disclosure, there is provided a technique, which includes: forming a film containing Si, O and N or a film containing Si and O on a substrate by performing a cycle a predetermined number of times under a condition where SiCl₄ is not gas-phase decomposed, the cycle including non-simultaneously performing: (a) forming NH termination on a surface of the substrate by supplying a first reactant containing N and H to the substrate; (b) forming a SiN layer having SiCl termination formed on its surface by supplying the SiCl₄ as a precursor to the substrate to react the NH termination formed on the surface of the substrate with the SiCl₄; and (c) reacting the SiN layer having the SiCl termination with a second reactant containing O by supplying the second reactant to the substrate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a vertical type process furnace of a substrate processing apparatus suitably used in an embodiment of the present disclosure, in which a portion of the process furnace is shown in a vertical cross sectional view.

FIG. 2 is a schematic configuration diagram of a vertical type process furnace of the substrate processing apparatus suitably used in an embodiment of the present disclosure, in which a portion of the process furnace is shown in a cross sectional view taken along line A-A in FIG. 1 .

FIG. 3 is a schematic configuration diagram of a controller of the substrate processing apparatus suitably used in an embodiment of the present disclosure, in which a control system of a controller is shown in a block diagram.

FIG. 4 is a diagram illustrating a film-forming sequence according to an embodiment of the present disclosure.

FIG. 5A illustrates a partial enlarged view of a surface of a substrate after a first reactant is supplied, FIG. 5B illustrates a partial enlarged view of a surface of a substrate after a precursor is supplied, and FIG. 5C illustrates a partial enlarged view of a surface of a substrate after a second reactant is supplied.

FIG. 6 is a model diagram illustrating a state of a surface of a substrate when a precursor is supplied.

FIG. 7 is a diagram illustrating an exemplary modification of a film-forming sequence according to an embodiment of the present disclosure.

FIG. 8 is a diagram illustrating an evaluation result of film thickness uniformity of a SiON film formed on a substrate in the plane of the substrate.

FIG. 9A is a diagram illustrating an evaluation result of film composition of the SiON film formed on the substrate, and FIG. 9B is a diagram illustrating an evaluation result of processing resistance of the SiON film formed on the substrate in FIG. 9A.

DETAILED DESCRIPTION Embodiment of the Present Disclosure

An embodiment of the present disclosure will now be described in detail mainly with reference to FIGS. 1 to 6 .

(1) Configuration of the Substrate Processing Apparatus

As illustrated in FIG. 1 , a process furnace 202 includes a heater 207 as a heating mechanism (temperature adjustment part). The heater 207 has a cylindrical shape and is supported by a holding plate so as to be vertically installed. The heater 207 functions as an activation mechanism (an excitation part) configured to thermally activate (excite) a gas.

A reaction tube 203 is disposed inside the heater 207 to be concentric with the heater 207. The reaction tube 203 is made of a heat resistant material, e.g., quartz (SiO₂), silicon carbide (SiC) or the like, and has a cylindrical shape with its upper end closed and its lower end opened. A process chamber 201 is formed in a hollow cylindrical portion of the reaction tube 203. The process chamber 201 is configured to accommodate wafers 200 as substrates. The processing of the wafers 200 is performed in the process chamber 201.

Nozzles 249 a and 249 b are installed in the process chamber 201 so as to penetrate a lower sidewall of the reaction tube 203. Gas supply pipes 232 a and 232 b are respectively connected to the nozzles 249 a and 249 b.

Mass flow controllers (MFCs) 241 a and 241 b, which are flow rate controllers (flow rate control parts), and valves 243 a and 243 b, which are opening/closing valves, are installed in the gas supply pipes 232 a and 232 b sequentially from the corresponding upstream sides of gas flow, respectively. A gas supply pipe 232 c is connected to the gas supply pipe 232 a at the downstream side of the valve 243 a. Gas supply pipes 232 d and 232 e are respectively connected to the gas supply pipe 232 b at the downstream side of the valve 243 b. MFCs 241 c, 241 d and 241 e and valves 243 c, 243 d and 243 e are respectively installed in the gas supply pipes 232 c, 232 d and 232 e sequentially from the corresponding upstream sides of gas flow.

As illustrated in FIG. 2 , the nozzles 249 a and 249 b are disposed in a space with an annular plan-view shape between the inner wall of the reaction tube 203 and the wafers 200 such that the nozzles 249 a and 249 b extend upward along an arrangement direction of the wafers 200 from a lower portion of the inner wall of the reaction tube 203 to an upper portion of the inner wall of the reaction tube 203. Specifically, the nozzles 249 a and 249 b are installed at a lateral side of a wafer arrangement region in which the wafers 200 are arranged, namely in a region which horizontally surrounds the wafer arrangement region, so as to extend along the wafer arrangement region. Gas supply holes 250 a and 250 b for supplying a gas are installed on the side surfaces of the nozzles 249 a and 249 b, respectively. The gas supply holes 250 a and 250 b are opened toward the center of the reaction tube 203 so as to allow a gas to be supplied toward the wafers 200. The gas supply holes 250 a and 250 b may be formed in a plural number between the lower portion of the reaction tube 203 and the upper portion of the reaction tube 203.

A precursor (precursor gas), for example, a chlorosilane-based gas which contains silicon (Si) and chlorine (Cl), is supplied from the gas supply pipe 232 a into the process chamber 201 via the MFC 241 a, the valve 243 a, and the nozzle 249 a. The precursor gas refers to a gaseous precursor, for example, a gas obtained by vaporizing a precursor which remains in a liquid state under a room temperature and an atmospheric pressure, or a precursor which remains in a gas state under a room temperature and an atmospheric pressure. As the chlorosilane-based gas, it may be possible to use, for example, a tetrachlorosilane (SiCl₄) gas. The SiCl₄ gas contains four chemical bonds (Si—Cl bonds) of Si and Cl in one molecule.

A hydrogen nitride-based gas containing, for example, nitrogen (N) and hydrogen (H), as a first reactant (nitriding agent), is supplied from the gas supply pipe 232 b into the process chamber 201 via the MFC 241 b, the valve 243 b, and the nozzle 249 b. As the hydrogen nitride-based gas, it may be possible to use, for example, an ammonia (NH₃) gas. The NH₃ gas contains three chemical bonds (N—H bonds) of N and H in one molecule.

A nitrogen (N₂) gas as an inert gas is supplied from the gas supply pipes 232 c and 232 d into the process chamber 201 via the MFCs 241 c and 241 d, the valves 243 c and 243 d, the gas supply pipes 232 a and 232 b, and the nozzles 249 a and 249 b. The N₂ gas acts as a purge gas, a carrier gas, a dilution gas, or the like.

An oxidizing gas containing, for example, oxygen (O), as a second reactant (oxidizing agent), is supplied from the gas supply pipe 232 e into the process chamber 201 via the MFC 241 e, the valve 243 e, the gas supply pipe 232 b, and the nozzle 249 b. As the oxidizing gas, it may be possible to use, for example, an oxygen (O₂) gas.

A precursor supply system is mainly configured by the gas supply pipe 232 a, the MFC 241 a, and the valve 243 a. A first reactant supply system is mainly configured by the gas supply pipe 232 b, the MFC 241 b, and the valve 243 b. An inert gas supply system is mainly configured by the gas supply pipes 232 c and 232 d, the MFCs 241 c and 241 d, and the valves 243 c and 243 d. A second reactant supply system is mainly configured by the gas supply pipe 232 e, the MFC 241 e, and the valve 243 e.

One or all of various supply systems described above may be configured as an integrated supply system 248 in which the valves 243 a to 243 e, the MFCs 241 a to 241 e, and the like are integrated. The integrated supply system 248 is connected to each of the gas supply pipes 232 a to 232 e so that a supply operation of various kinds of gases into the gas supply pipes 232 a to 232 e, i.e., an opening/closing operation of the valves 243 a to 243 e, a flow rate adjusting operation by the MFCs 241 a to 241 e or the like, is controlled by a controller 121 which will be described later. The integrated supply system 248 is configured as an integral type or division type integrated unit, and is also configured so that it is detachable from the gas supply pipes 232 a to 232 e or the like, so as to perform maintenance, replacement, expansion or the like of the integrated supply system 248, on an integrated unit basis.

An exhaust pipe 231 configured to exhaust an internal atmosphere of the process chamber 201 is installed at a lower side of the sidewall of the reaction tube 203. A vacuum pump 246 as a vacuum exhaust device is connected to the exhaust pipe 231 via a pressure sensor 245 as a pressure detector (pressure detection part) which detects the internal pressure of the process chamber 201 and an auto pressure controller (APC) valve 244 as a pressure regulator (pressure regulation part). The APC valve 244 is configured so that a vacuum exhaust and a vacuum exhaust stop of the interior of the process chamber 201 can be performed by opening and closing the APC valve 244 while operating the vacuum pump 246 and so that the internal pressure of the process chamber 201 can be adjusted by adjusting an opening degree of the APC valve 244 based on pressure information detected by the pressure sensor 245 while operating the vacuum pump 246. An exhaust system mainly includes the exhaust pipe 231, the pressure sensor 245 and the APC valve 244. The vacuum pump 246 may be regarded as being included in the exhaust system.

A seal cap 219, which serves as a furnace opening cover configured to hermetically seal a lower end opening of the reaction tube 203, is installed under the reaction tube 203. The seal cap 219 is made of a metal material such as, e.g., stainless steel (SUS) or the like, and is formed in a disc shape. An O-ring 220, which is a seal member making contact with the lower end portion of the reaction tube 203, is installed on an upper surface of the seal cap 219. A rotation mechanism 267 configured to rotate a boat 217, which will be described later, is installed under the seal cap 219. A rotary shaft 255 of the rotation mechanism 267, which penetrates the seal cap 219, is connected to the boat 217. The rotation mechanism 267 is configured to rotate the wafers 200 by rotating the boat 217. The seal cap 219 is configured to be vertically moved up and down by a boat elevator 115 which is an elevator mechanism installed outside the reaction tube 203. The boat elevator 215 is configured as a transfer device (transfer mechanism) which loads and unloads (transfers) the wafers 200 into and from (out of) the process chamber 201 by moving the seal cap 219 up and down.

The boat 217 serving as a substrate support is configured to support a plurality of wafers 200, e.g., 25 to 200 wafers, in such a state that the wafers 200 are arranged in a horizontal posture and in multiple stages along a vertical direction with the centers of the wafers 200 aligned with one another. That is, the boat 217 is configured to arrange the wafers 200 in a spaced-apart relationship. The boat 217 is made of a heat resistant material such as quartz or SiC. Heat insulating plates 218 made of a heat resistant material such as quartz or SiC are supported below the boat 217 in a horizontal posture and in multiple stages.

A temperature sensor 263 serving as a temperature detector is installed in the reaction tube 203. Based on temperature information detected by the temperature sensor 263, a state of supplying electric power to the heater 207 is adjusted such that the interior of the process chamber 201 has a desired temperature distribution. The temperature sensor 263 is installed along the inner wall of the reaction tube 203.

As illustrated in FIG. 3 , the controller 121, which is a controller (control means), may be configured as a computer including a central processing unit (CPU) 121 a, a random access memory (RAM) 121 b, a memory device 121 c, and an I/O port 121 d. The RAM 121 b, the memory device 121 c and the I/O port 121 d are configured to exchange data with the CPU 121 a via an internal bus 121 e. An input/output device 122 constituted by, e.g., a touch panel or the like, is connected to the controller 121.

The memory device 121 c is constituted by, for example, a flash memory, a hard disk drive (HDD), or the like. A control program for controlling operations of a substrate processing apparatus, a process recipe for specifying sequences and conditions of a film-forming process as described hereinbelow, or the like is readably stored in the memory device 121 c. The process recipe functions as a program for causing the controller 121 to execute each sequence in the film-forming process, as described hereinbelow, to obtain a predetermined result. Hereinafter, the process recipe and the control program will be generally and simply referred to as a “program.” Further, the process recipe will be simply referred to as a “recipe.” When the term “program” is used herein, it may indicate a case of including only the recipe, a case of including only the control program, or a case of including both the recipe and the control program. The RAM 121 b is configured as a memory area (work area) in which a program, data and the like read by the CPU 121 a is temporarily stored.

The I/O port 121 d is connected to the MFCs 241 a to 241 e, the valves 243 a to 243 e, the pressure sensor 245, the APC valve 244, the vacuum pump 246, the temperature sensor 263, the heater 207, the rotation mechanism 267, the boat elevator 115, and the like, as described above.

The CPU 121 a is configured to read the control program from the memory device 121 c and execute the same. The CPU 121 a also reads the recipe from the memory device 121 c according to an input of an operation command from the input/output device 122. In addition, the CPU 121 a is configured to control, according to the contents of the recipe thus read, the flow rate adjusting operation of various kinds of gases by the MFCs 241 a to 241 e, the opening/closing operation of the valves 243 a to 243 e, the opening/closing operation of the APC valve 244, the pressure regulating operation performed by the APC valve 244 based on the pressure sensor 245, the driving and stopping of the vacuum pump 246, the temperature adjusting operation performed by the heater 207 based on the temperature sensor 263, the operation of rotating the boat 217 with the rotation mechanism 267 and adjusting the rotation speed of the boat 217, the operation of moving the boat 217 up and down with the boat elevator 115, and the like.

The controller 121 may be configured by installing, on the computer, the aforementioned program stored in an external memory device 123. The external memory device 123 may include, for example, a magnetic disc such as an HDD, an optical disc such as a CD, a magneto-optical disc such as an MO, a semiconductor memory such as a USB memory, and the like. The memory device 121 c or the external memory device 123 is configured as a computer-readable recording medium. Hereinafter, the memory device 121 c and the external memory device 123 will be generally and simply referred to as a “recording medium.” When the term “recording medium” is used herein, it may indicate a case of including only the memory device 121 c, a case of including only the external memory device 123, or a case of including both the memory device 121 c and the external memory device 123. Further, the program may be supplied to the computer using a communication means such as the Internet or a dedicated line, instead of using the external memory device 123.

(2) Substrate Processing

A substrate processing sequence example of forming a SiON film on a wafer 200 as a substrate using the aforementioned substrate processing apparatus, i.e., a film-forming sequence example, which is one of the processes for manufacturing a semiconductor device, will be described with reference to FIG. 4 . In the following descriptions, the operations of the respective parts constituting the substrate processing apparatus are controlled by the controller 121.

In the film-forming sequence illustrated in FIG. 4 , there are performed: step A of supplying an NH₃ gas as a first reactant containing N and H to a wafer 200 to form NH termination on a surface of the wafer 200; step B of supplying an NH₃ gas as a first reactant containing N and H to the wafer 200 to form NH termination on a surface of the wafer 200; step C of supplying a SiCl₄ gas as a precursor to the wafer 200 to react the NH termination formed on the surface of the wafer 200 with SiCl₄ to form a SiN layer having SiCl termination formed on its surface; and step D of supplying an O₂ gas as a second reactant containing O to the wafer 200 to react the SiN layer having SiCl termination with the O₂ gas.

Specifically, a cycle which non-simultaneously performs step B, step C, and step D described above under a condition in which SiCl₄ is not gas-phase decomposed after performing step A described above is implemented a predetermined number of times. Thus, a SiON film is formed on the wafer 200. Furthermore, in FIG. 4 , execution periods of steps A, B, C, and D are denoted as A, B, C, and D, respectively.

In the present disclosure, for the sake of convenience, the film-forming sequence illustrated in FIG. 4 may sometimes be denoted as follows. Here, P indicates a purge step of supplying a purge gas to the wafer 200 to remove the gas or the like remaining on the wafer 200. The same denotation will be used in other embodiments and the like as described hereinbelow.

NH₃→P→(NH₃→P→SiCl₄→P→O₂→P)×n⇒SiON

When the term “wafer” is used herein, it may refer to a wafer itself or a laminated body of a wafer and a predetermined layer or film formed on the surface of the wafer. In addition, when the phrase “a surface of a wafer” is used herein, it may refer to a surface of a wafer itself or a surface of a predetermined layer or the like formed on a wafer. Furthermore, in the present disclosure, the expression “a predetermined layer is formed on a wafer” may mean that a predetermined layer is directly formed on a surface of a wafer itself or that a predetermined layer is formed on a layer or the like formed on a wafer. In addition, when the term “substrate” is used herein, it may be synonymous with the term “wafer.”

(Wafer Charging and Boat Loading)

A plurality of wafers 200 is charged on the boat 217 (wafer charging). Thereafter, as illustrated in FIG. 1 , the boat 217 supporting the plurality of wafers 200 is lifted up by the boat elevator 115 and is loaded into the process chamber 201 (boat loading). In this state, the seal cap 219 seals the lower end of the reaction tube 203 through the O-ring 220.

(Pressure Regulation and Temperature Adjustment)

The interior of the process chamber 201, namely the space in which the wafers 200 are located, is vacuum-exhausted (depressurization-exhausted) by the vacuum pump 246 so as to reach a desired processing pressure (degree of vacuum). In this operation, the internal pressure of the process chamber 201 is measured by the pressure sensor 245. The APC valve 244 is feedback-controlled based on the measured pressure information. Furthermore, the wafers 200 in the process chamber 201 are heated by the heater 207 to a desired processing temperature (film-forming temperature). In this operation, the state of supplying electric power to the heater 207 is feedback-controlled based on the temperature information detected by the temperature sensor 263 such that the interior of the process chamber 201 has a desired temperature distribution. In addition, the rotation of the wafers 200 by the rotation mechanism 267 begins. The driving of the vacuum pump 246 and the heating and rotation of the wafers 200 may be all continuously performed at least until the processing of the wafers 200 is completed.

(Film-Forming Process)

Next, the following steps A to D are sequentially performed.

[Step A]

At this step, an NH₃ gas is supplied to the wafer 200 in the process chamber 201. Specifically, the valve 243 b is opened to allow an NH₃ gas to flow through the gas supply pipe 232 b. The flow rate of the NH₃ gas is adjusted by the MFC 241 b. The NH₃ gas is supplied into the process chamber 201 via the nozzle 249 b and is exhausted from the exhaust pipe 231. At this time, the NH₃ gas is supplied to the wafer 200 from the side of the wafer 200. Simultaneously, the valves 243 c and 243 d may be opened to allow an N₂ gas to flow through the gas supply pipes 232 c and 232 d.

The processing conditions at this step may be exemplified as follows:

-   -   NH₃ gas supply flow rate: 100 to 10,000 sccm     -   N₂ gas supply flow rate (per gas supply pipe): 0 to 10,000 sccm     -   Supply time of each gas: 1 to 30 minutes     -   Processing temperature: 300 to 1,000 degrees C., 700 to 900         degrees C. in some embodiments, or 750 to 800 degrees C. in some         embodiments     -   Processing pressure: 1 to 4,000 Pa or 20 to 1,333 Pa in some         embodiments.

Furthermore, in the present disclosure, the expression of the numerical range such as “300 to 1,000 degrees C.” may mean that a lower limit value and an upper limit value are included in that range. Therefore, “300 to 1,000 degrees C.” may mean “300 degrees C. or higher and 1,000 degrees C. or lower.” The same applies to other numerical ranges.

A natural oxide film or the like may be formed on the surface of the wafer 200 prior to performing a film-forming process. By supplying the NH₃ gas to the wafer 200 under the aforementioned conditions, NH termination can be formed on the surface of the wafer 200 on which the natural oxide film or the like is formed. The NH termination formed on the surface of the wafer 200 may be regarded as synonymous with an H termination. Furthermore, since the supply of the NH₃ gas to the wafer 200 and the process of forming the NH termination on the surface of the wafer 200 at this step are performed prior to a substantial film-forming process (steps B, C and D), they will be referred to as pre-flow and pre-processing, respectively.

In the case where the NH₃ gas is supplied to the wafer 200 from the side of the wafer 200 as in the present embodiment, there is a tendency that the formation of the NH termination starts earlier in an outer peripheral portion of the wafer 200, and starts in the central portion of the wafer 200 with delay. This phenomenon becomes particularly conspicuous when a pattern including a recess such as a trench or a hole is formed on the surface of the wafer 200. At this step, if the supply time of the NH₃ gas is less than 1 minute, although the NH termination may be formed in the outer peripheral portion of the wafer 200, the NH termination may be difficult to be formed in the center portion of the wafer 200 (loading effect). By setting the supply time of the NH₃ gas at a time of 1 minute or more, it is possible to form the NH termination from the outer peripheral portion to the central portion of the wafer 200 uniformly, i.e., substantially uniformly in amount and density. However, if the supply time of the NH₃ gas exceeds 30 minutes, the supply of the NH₃ gas to the wafer 200 may be continued in a state in which the formation reaction of the NH termination on the surface of the wafer 200 is saturated. As a result, usage amount of the NH₃ gas which does not contribute to the formation of the NH termination unnecessarily increases, which may increase a gas cost. By setting the supply time of the NH₃ gas at a time of 30 minutes or less, it is possible to suppress an increase in the gas cost.

After the NH termination is formed on the surface of the wafer 200 by pre-flowing the NH₃ gas to the wafer 200, the valve 243 b is closed to stop the supply of the NH₃ gas into the process chamber 201. Then, the interior of the process chamber 201 is vacuum-exhausted and the gas or the like remaining within the process chamber 201 is removed from the interior of the process chamber 201. At this time, the valves 243 c and 243 d are opened to supply an N₂ gas as a purge gas into the process chamber 201 (purge step). The processing pressure at the purge step may be set at a pressure of, for example, 1 to 100 Pa, and the supply flow rate of the N₂ gas may be set at a flow rate of, for example, 10 to 10,000 sccm.

As the first reactant, it may be possible to use, in addition to the NH₃ gas, a hydrogen nitride-based gas such as a diazene (N₂H₂) gas, a hydrazine (N₂H₄) gas, and an N₃H₈ gas.

As the inert gas, it may be possible to use, in addition to the N₂ gas, a rare gas such as an Ar gas, an He gas, an Ne gas, and an Xe gas. This also applies to steps B, C, and D as described hereinbelow.

[Step B]

At this step, an NH₃ gas is supplied to the wafer 200 in the process chamber 201 as at step A. Specifically, the opening/closing control of the valves 243 a to 243 d is performed in the same procedure as the opening/closing control of the valves 243 b to 243 d at step A. The flow rate of the NH₃ gas is controlled by the MFC 241 b. The NH₃ gas is supplied into the process chamber 201 via the nozzle 249 b and is exhausted from the exhaust pipe 231. At this time, the NH₃ gas is supplied to the wafer 200 from the side of the wafer 200.

The processing conditions at this step may be exemplified as follows:

Supply time of NH₃ gas: 1 to 60 seconds, or 1 to 50 seconds in some embodiments.

Other processing conditions may be similar to the processing conditions of step A.

By supplying the NH₃ gas to the wafer 200 under the aforementioned conditions, NH termination is formed on the surface of the wafer 200 as at step A. Thus, a desired film-forming reaction can go ahead on the wafer 200 at step C as described hereinbelow. A partial enlarged view of the surface of the wafer 200 in which the NH termination is formed is illustrated in FIG. 5A. As described above, the NH termination formed on the surface of the wafer 200 may be regarded as synonymous with an H termination. Furthermore, at step B in a first cycle, the process of forming the NH termination on the surface of the wafer 200 performed at step A is complemented. At step B after a second cycle, a process of forming the NH termination on a surface of a SiON layer as described hereinbelow is performed.

After the NH termination is formed on the surface of the wafer 200, the valve 243 b is closed to stop the supply of the NH₃ gas into the process chamber 201. Then, the gas or the like remaining within the process chamber 201 is removed from the interior of the process chamber 201 under the same processing procedures and processing conditions as those of the purge step of step A described above.

As the gas used at this step, it may be possible to use, in addition to the NH₃ gas, various kinds of hydrogen nitride-based gases exemplified at step A described above. Furthermore, it may be possible to use different gases at step A and step B. For example, it may be possible to use the NH₃ gas at step A and the N₂H₂ gas at step B.

[Step C]

At this step, a SiCl₄ gas is supplied to the wafer 200 in the process chamber 201, namely the NH termination formed on the surface of the wafer 200. Specifically, the opening/closing control of the valves 243 a, 243 c and 243 d is performed in the same procedure as the opening/closing control of the valves 243 b to 243 d at step A. The flow rate of the SiCl₄ gas is controlled by the MFC 241 a. The SiCl₄ gas is supplied into the process chamber 201 via the nozzle 249 a and is exhausted from the exhaust pipe 231. At this time, the SiCl₄ gas is supplied to the wafer 200 from the side of the wafer 200.

The processing conditions at this step may be exemplified as follows:

-   -   SiCl₄ gas supply flow rate: 10 to 2,000 sccm, or 100 to 1,000         sccm in some embodiments     -   Supply time of SiCl₄ gas: 60 to 180 seconds, or 60 to 120         seconds in some embodiments     -   Processing temperature: 300 to 1,000 degrees C., 700 to 900         degrees C. in some embodiments, or 750 to 800 degrees C. in some         embodiments     -   Processing pressure: 1 to 2,000 Pa, or 20 to 1,333 Pa in some         embodiments.

Other processing conditions may be similar to the processing conditions of step A.

By supplying the SiCl₄ gas to the wafer 200 under the aforementioned conditions, it is possible to react the NH termination formed on the surface of the wafer 200 with SiCl₄. Specifically, as illustrated in FIG. 6 , Si—Cl bonds in SiCl₄ and N—H bonds in the NH termination formed on the surface of the wafer 200 can be broken. Furthermore, Si after the Si—Cl bonds in SiCl₄ are broken can be bonded to N after the N—H bonds in the NH termination formed on the surface of the wafer 200 are broken to form Si—N bonds. Cl separated from Si and H separated from N respectively constitute gaseous substances such as HCl or the like so as to be desorbed from the wafer 200 and are exhausted from the exhaust pipe 231.

In addition, at this step, the Si—Cl bonds, which are not converted into the Si—N bonds among the Si—Cl bonds in SiCl₄ during the aforementioned reaction, can be held without being broken. That is, at this step, Si after the Si—Cl bonds in SiCl₄ are broken can be bonded to N after the N—H bonds in the NH termination formed on the surface of the wafer 200 are broken in a state where Cl is bonded to each of three bonding hands of four bonding hands of Si constituting SiCl₄.

In the present disclosure, the aforementioned reaction proceeding on the surface of the wafer 200 at step C will be referred to as an adsorptive substitution reaction. At this step, the adsorptive substitution reaction described above can proceed to form a layer which contains Si and N and whose entire surface is terminated with SiCl, i.e., a silicon nitride layer (SiN layer) having SiCl termination formed on its surface, on the wafer 200. A partial enlarged view of the surface of the wafer 200 on which the SiN layer having SiCl termination is formed is illustrated in FIG. 5B. Furthermore, in FIG. 5B, illustration of part of Cl is omitted for the sake of convenience. The SiN layer having SiCl termination becomes a layer in which further Si deposition on the wafer 200 does not go ahead even if the supply of the SiCl₄ gas to the wafer 200 is further continued after the formation of this layer, due to Cl constituting the SiCl termination acting as steric hindrance. That is, the SiN layer having SiCl termination becomes a layer to which self-limitation is applied for further Si adsorption reaction. Accordingly, the thickness of the SiN layer becomes a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer. Furthermore, the SiCl termination formed on the surface of the wafer 200 may be regarded as synonymous with a Cl termination.

The processing conditions at this step are conditions under which SiCl₄ supplied into the process chamber 201 is not gas-phase decomposed (pyrolyzed). That is, the aforementioned processing conditions are conditions under which SiCl₄ supplied into the process chamber 201 does not generate an intermediate in the gas phase and the Si deposition on the wafer 200 by the gas-phase reaction does not go ahead. In other words, the processing conditions described above are conditions under which only the adsorptive substitution reaction described above can occur on the wafer 200. By setting the processing conditions at this step to such conditions, it is possible to allow the SiN layer formed on the wafer 200 to become a layer having excellent thickness uniformity in the plane of the wafer (hereinafter, also simply referred to as in-plane thickness uniformity).

If the film-forming temperature (processing temperature) is lower than 300 degrees C., there may be a case where it is difficult for the SiN layer to be formed on the wafer 200 and for the formation of the SiN film on the wafer 200 to go ahead at a practical deposition rate. Furthermore, a large amount of impurity such as Cl or the like may remain in the SiN film formed on the wafer 200, lowering a processing resistance of the SiN film. By setting the film-forming temperature at a temperature of 300 degree C. or higher, the formation of the SiN film on the wafer 200 can go ahead at a practical deposition rate. In addition, it is possible to allow the SiN film formed on the wafer 200 to become a film having low impurity concentration and excellent processing resistance. By setting the film-forming temperature at a temperature of 700 degrees C. or higher, it is possible to reliably achieve the aforementioned effects. By setting the film-forming temperature at a temperature of 750 degrees C. or higher, it is possible to more reliably achieve the aforementioned effects.

If the film-forming temperature exceeds 1,000 degrees C., there may be a case where a reaction other than the aforementioned adsorptive substitution reaction goes ahead in the process chamber 201. For example, the Si—Cl bonds which are not converted into the Si—N bonds among the Si—Cl bonds in SiCl₄ may be broken, making it difficult to be SiCl-terminated on the entire surface of the SiN layer. That is, it may be difficult for the SiN layer to become a layer to which self-limitation is applied for further Si adsorption reaction. In addition, SiCl₄ supplied into the process chamber 201 is gas-phase decomposed (pyrolyzed) to generate an intermediate, and the Si deposition on the wafer 200 by the gas-phase reaction may go ahead. As a result, the in-plane thickness uniformity of the SiN layer formed on the wafer 200, i.e., the film thickness uniformity of the SiN film in the plane of the substrate (hereinafter, simply referred to as in-plane film thickness uniformity), may be deteriorated. By setting the film-forming temperature at a temperature of 1,000 degrees C. or lower, it is possible to cope with the situations described above. By setting the film-forming temperature at a temperature of 900 degrees C. or lower, it is possible to reliably cope with the situations described above. By setting the film-forming temperature at a temperature of 800 degrees C. or lower, it is possible to more reliably solve the problems described above.

From these facts, the film-forming temperature may be set at 300 to 1,000 degrees C., 700 to 900 degrees C. in some embodiments, or 750 to 800 degrees C. in some embodiments. Furthermore, among the temperature conditions illustrated above, the relatively high temperature condition such as, e.g., 700 to 900 degrees C., is a temperature condition under which a chlorosilane-based gas such as a dichlorosilane (SiH₂Cl₂, abbreviation: DCS) gas, a hexachlorodisilane (Si₂Cl₆, abbreviation: HCDS) gas or the like is gas-phase decomposed. That is, the DCS gas or HCDS gas may be gas-phase decomposed at 700 to 900 degrees C., and when the DCS gas or HCDS gas is supplied to the wafer 200 from the side of the wafer 200, the outer peripheral portion of the wafer 200 becomes thick and the gas does not reach the central portion thereof, making it difficult to achieve the film thickness uniformity. On the other hand, the SiCl₄ gas is not gas-phase decomposed even under a high temperature condition in which the DCS gas or the HCDS gas is gas-phase decomposed. Therefore, when performing the film-forming process at this relatively high temperature zone, it can be said that the SiCl₄ gas is a precursor capable of enhancing the thickness controllability of the SiN film formed on the wafer 200.

In the case where the SiCl₄ gas is supplied to the wafer 200 from the side of the wafer 200 as in the present embodiment, there is a tendency that the formation of the SiN layer starts earlier in the outer peripheral portion of the wafer 200, and starts in the central portion of the wafer 200 with delay. This phenomenon becomes particularly conspicuous when the aforementioned pattern is formed on the surface of the wafer 200. At this step, if the supply time of the SiCl₄ gas is less than 60 seconds, although the SiN layer may be formed in the outer peripheral portion of the wafer 200, the SiN layer may be difficult to be formed in the central portion of the wafer 200. By setting the supply time of the SiCl₄ gas at a time of 60 seconds or more, it is possible to form the SiN layer substantially uniformly, i.e., substantially uniformly in thickness and composition, from the outer peripheral portion to the central portion of the wafer 200. However, if the supply time of the SiCl₄ gas exceeds 180 seconds, the supply of the SiCl₄ gas to the wafer 200 may be continued in a state in which the formation reaction of the SiN layer on the surface of the wafer 200 is saturated. As a result, the usage amount of the SiCl₄ gas which does not contribute to the formation of the SiN layer unnecessarily increases, which may increase the gas cost. By setting the supply time of the SiCl₄ gas at a time of 180 seconds or less, it is possible to suppress an increase in gas cost. By setting the supply time of the SiCl₄ gas at a time of 120 seconds or less, it is possible to reliably suppress an increase in gas cost.

After the SiN layer is formed on the wafer 200, the valve 243 a is closed to stop the supply of the SiCl₄ gas into the process chamber 201. Then, the gas or the like remaining within the process chamber 201 is removed from the interior of the process chamber 201 under the same processing procedures and processing conditions as those of the purge step of step A described above.

[Step D]

At this step, an O₂ gas is supplied to the wafer 200 in the process chamber 201, i.e., the SiN layer having SiCl termination formed on the wafer 200. Specifically, the opening/closing control of the valves 243 e, 243 c, and 243 d is performed in the same procedure as the opening/closing control of the valves 243 b to 243 d at step A. The flow rate of the O₂ gas is controlled by the MFC 241 e. The O₂ gas is supplied into the process chamber 201 via the nozzle 249 b and is exhausted from the exhaust pipe 231. At this time, the O₂ gas in a non-plasma-excited state is supplied to the wafer 200 from the side of the wafer 200. That is, the O₂ gas thermally excited in a non-plasma atmosphere is supplied to the wafer 200 from the side of the wafer 200.

The processing conditions at this step may be exemplified as follows:

-   -   O₂ gas supply flow rate: 100 to 10,000 sccm     -   Supply time of O₂ gas: 1 to 120 seconds, or 1 to 50 seconds in         some embodiments.

Other processing conditions may be similar to the processing conditions of step A.

By supplying the O₂ gas to the wafer 200 under the aforementioned conditions, it is possible to modify (oxidize) at least a portion of the SiN layer having SiCl termination formed on the wafer 200 at step C. That is, at least a portion of O components contained in the O₂ gas can be added to the SiN layer having SiCl termination to form Si—O bonds in the SiN layer having SiCl termination. The SiN layer having SiCl termination is modified (oxidized) to form a silicon oxynitride layer (SiON layer), which is a layer containing Si, O and N, on the wafer 200. A partial enlarged view of the surface of the wafer 200 on which the SiON layer is formed is illustrated in FIG. 5C. Furthermore, by adjusting the supply time of the O₂ gas, it is possible to adjust the N concentration in the SiON layer.

When forming the SiON layer, Cl contained in the SiN layer having SiCl termination constitutes a gaseous substance containing at least Cl during the modification reaction by the O₂ gas, and is discharged from the process chamber 201. That is, an impurity such as Cl in the SiN layer having SiCl termination is separated from the SiN layer having SiCl termination by being drawn out or desorbed from the SiN layer having SiCl termination. In other words, the impurity such as Cl is separated from the SiN layer, constitutes a gaseous substance such as NH_(x)Cl_(y) or NO_(x) and desorbs from the wafer 200, and is exhausted from the exhaust pipe 231. Thus, the SiON layer becomes a layer having a small amount of impurity such as Cl, compared with the SiN layer having SiCl termination.

After the SiON layer is formed, the valve 243 e is closed to stop the supply of the O₂ gas into the process chamber 201. Then, the gas or the like remaining within the process chamber 201 is removed from the interior of the process chamber 201 under the same processing procedures and processing conditions as those of the purge step of step A described above.

As the second reactant, it may be possible to use, in addition to the O₂ gas, a non-plasma-excited O-containing gas such as a nitrogen monoxide (NO) gas, a nitrous oxide (N₂O) gas, a nitrogen dioxide (NO₂) gas, a carbon monoxide (CO) gas, a carbon dioxide (CO₂) gas, water vapor (H₂O gas) or the like.

[Performing a Predetermined Number of Times]

After step A is performed, a cycle which non-simultaneously, i.e., non-synchronously, performs steps B, C, and D is implemented a predetermined number of times (n times, where n is an integer of 1 or more), whereby a SiON film having a predetermined thickness can be formed on the wafer 200. Furthermore, the aforementioned cycle may be repeated multiple times. That is, the thickness of the SiON layer formed when the cycle which non-simultaneously performs steps B, C, and D is implemented once may be set smaller than a desired thickness, and the aforementioned cycle may be repeated multiple times until the thickness of the SiON film formed by laminating the SiON layer becomes equal to the desired thickness.

Furthermore, in order to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity, the supply time of the SiCl₄ gas at step C may be set such that the thickness of the SiN layer formed in the central portion of the wafer 200 becomes substantially equal to the thickness of the SiN layer formed in the outer peripheral portion of the wafer 200 in some embodiments. In other words, the supply time of the SiCl₄ gas at step C may be set for a time so that the amount of the adsorptive substitution reaction occurring between the NH termination formed on the surface of the wafer 200 and the SiCl₄ gas in the central portion of the wafer 200 becomes substantially equal to the amount of the adsorptive substitution reaction occurring between the NH termination formed on the surface of the wafer 200 and the SiCl₄ gas in the outer peripheral portion of the wafer 200 in some embodiments. For example, by setting the supply time of the SiCl₄ gas at step C longer than the supply time of the NH₃ gas at step B, it is possible to reliably achieve the operational effects described above.

Furthermore, in order to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity, the supply time of the NH₃ gas at step A may be set for a time so that the amount or density of the NH termination formed in the central portion of the wafer 200 becomes substantially equal to the amount or density of the NH termination formed in the outer peripheral portion of the wafer 200 in some embodiments. For example, by setting the supply time of the NH₃ gas at step A longer than the supply time of the NH₃ gas at step B, it is possible to reliably achieve the operational effects described above. In addition, for example, by setting the supply time of the NH₃ gas at step A longer than the supply time of the SiCl₄ gas at step C, it is possible to more reliably achieve the operational effects described above.

From this fact, the supply time of the NH₃ gas at step A may be set longer than the supply time of the SiCl₄ gas at step C, and the supply time of the SiCl₄ gas at step C may be set longer than the supply time of the NH₃ gas at step B in some embodiments. Furthermore, the supply time of the O₂ gas at step D may be set shorter than the supply time of the NH₃ gas at step A and longer than the supply time of the NH₃ gas at step B in some embodiments. By setting the supply times of the various kinds of gases at steps A, B, C, and D to have such a balance, it is possible to allow the SiON film formed on the wafer 200 to become a film having very excellent in-plane film thickness uniformity.

(After-Purge and Atmospheric Pressure Return)

After the aforementioned film-forming process is completed, the N₂ gas is supplied from the respective gas supply pipes 232 c and 232 d into the process chamber 201 and is exhausted from the exhaust pipe 231. Thus, the interior of the process chamber 201 is purged and the gas or the reaction byproduct, which remains within the process chamber 201, is removed from the interior of the process chamber 201 (after-purge). Thereafter, the internal atmosphere of the process chamber 201 is substituted by an inert gas (inert gas substitution). The internal pressure of the process chamber 201 is returned to an atmospheric pressure (atmospheric pressure return).

(Boat Unloading and Wafer Discharging)

Thereafter, the seal cap 219 is moved down by the boat elevator 115 to open the lower end of the reaction tube 203. Then, the processed wafers 200 supported on the boat 217 are unloaded from the lower end of the reaction tube 203 to the outside of the reaction tube 203 (boat unloading). The processed wafers 200 are discharged from the boat 217 (wafer discharging).

(3) Effects According to the Present Embodiment

According to the present embodiment, one or more effects as set forth below may be achieved.

(a) By implementing a cycle a predetermined number of times under the condition where SiCl₄ is not gas-phase decomposed after performing step A, the cycle including non-simultaneously performing step B, step C and step D, it is possible to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity.

This is because, by performing step C under the aforementioned conditions, i.e., under the conditions in which only the adsorptive substitution reaction occurs between the NH termination formed on the surface of the wafer 200 and SiCl₄, it is possible to allow the SiN layer formed on the wafer 200 to become a layer whose entire surface is terminated with SiCl. That is, it is possible to allow the SiN layer to become a layer to which self-limitation is applied for further Si adsorption reaction, i.e., for further adsorptive substitution reaction. As a result, it is possible to allow the SiN layer formed on the wafer 200 to become a layer having excellent in-plane thickness uniformity. This also makes it possible to allow the SiON layer formed by modifying (oxidizing) the SiN layer to become a layer having excellent in-plane thickness uniformity at subsequent step D.

As described above, according to the present embodiment, only the NH termination formed on the wafer 200 and the SiCl termination formed on the wafer 200 can be allowed to utilize a film-forming mechanism which contributes to the formation of the SiON film on the wafer 200. As a result, it is possible to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity.

(b) By setting the supply time of the SiCl₄ gas at step C longer than the supply time of the NH₃ gas at step B, it is possible to allow the SiN layer having SiCl termination formed on its surface formed on the wafer 200 to become a layer having excellent in-plane thickness uniformity. As a result, it is possible to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity. That is, it is possible to improve the loading effect (substrate surface area dependency).

(c) By setting the supply time of the NH₃ gas at step A longer than the supply time of the NH₃ gas at step B, it is possible to uniformly form the NH termination from the outer peripheral portion to the central portion of the surface of the wafer 200 before the substantial film-forming process. This makes it possible to allow the SiN layer formed on the wafer 200 to become a layer having excellent in-plane thickness uniformity. As a result, it is possible to allow the SiON film formed on the wafer 200 to become a film having excellent in-plane film thickness uniformity.

In addition, by setting the supply time of the NH₃ gas at step A longer than the supply time of the SiCl₄ gas at step C, it is possible to more reliably achieve the aforementioned effects.

Furthermore, by setting the supply time of the NH₃ gas at step A longer than the supply time of the O₂ gas at step D, it is possible to more reliably achieve the aforementioned effects.

(d) Since the SiCl₄ gas is used as the precursor, although step C is performed under a relatively high temperature condition (temperature condition of 700 degrees C. or higher) in which the DCS gas or HCDS gas is gas-phase decomposed, it is possible to allow the thickness of the SiN layer formed at that time to become a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer. Therefore, it is possible to precisely and stably control the thickness of the SiON film even under a relatively high temperature condition. That is, it is possible to allow the formation of the SiON film on the wafer 200 to go ahead with enhanced controllability even under a relatively high temperature condition and to improve the processing resistance (HF resistance) of the SiON film as a high temperature is possible.

Furthermore, when the DCS gas or HCDS gas is used as the precursor, for example, under a relatively high temperature condition of 700 degrees C. or higher, the precursor is gas-phase decomposed and the Si-containing layer formed on the wafer 200 by supplying the precursor becomes a layer to which self-limitation is not applied for further Si adsorption reaction. Therefore, it is difficult to allow the thickness of the Si-containing layer formed by supplying these precursors to become a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer under a relatively high temperature condition. That is, when these precursors are used, the gas-phase reaction becomes dominant and an excess gas-phase reaction occurs under a relatively high temperature condition, making it impossible to improve the loading effect. As a result, it is difficult to precisely and stably control the thickness of the finally obtained SiON film. Furthermore, although the film thickness uniformity is achieved by film formation under the temperature conditions in which the precursors are not gas-phase decomposed, the processing resistance (HF resistance) may be deteriorated compared with the present disclosure.

(e) By using the second reactant in a non-plasma-excited state at step D, it is possible to suppress oxidation of the SiN layer having SiCl termination formed at step C, and to easily partially remain N without completely desorbing N from the SiN layer. This makes it possible to form the SiON film of an appropriate composition on the wafer 200.

In addition, by controlling the oxidizing gas supply conditions such as the supply time of the O₂ gas, the supply flow rate of the O₂ gas, the processing pressure, and the type of the oxidizing gas at step D, it is possible to control the composition ratio of O and N in the SiON film. This makes it possible to control the processing resistance (HF resistance) of the SiON film as formed.

(f) The effects mentioned above can be similarly achieved in the case where the aforementioned hydrogen nitride-based gas other than the NH₃ gas is used as the first reactant, or in the case where the aforementioned oxidizing gas other than the O₂ gas is used as the second reactant, or in the case where the aforementioned inert gas other than the N₂ gas is used.

Other Embodiments

While the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the aforementioned embodiment but may be variously modified without departing from the spirit of the present disclosure.

For example, the purge step after the pre-flow of the NH₃ gas at step A (purge step between the pre-flow of the NH₃ gas at step A and the supply of the NH₃ gas at step B) may be omitted. That is, as illustrated in FIG. 7 or in the following film-forming sequence example, the pre-flow of the NH₃ gas at step A and the supply of the NH₃ gas at step B may be continuously performed. Thus, the same effects as those of the film-forming sequence illustrated in FIG. 4 can be achieved, and further, the total processing time can be shortened and the productivity can be improved.

NH₃→(NH₃→P→SiCl₄→P→O₂→P)×n⇒SiON

Furthermore, for example, at at least one of step A and step B, a plasma-activated (excited) NH₃ gas, i.e., a first reactant in a plasma-excited state, may be supplied to the wafer 200. Even in this case, the same effects as those of the film-forming sequence illustrated in FIG. 4 may be achieved.

In addition, for example, at step D, a plasma-activated (excited) O₂ gas, i.e., a second reactant in a plasma-excited state, may be supplied. Even in this case, the same effects as those of the film-forming sequence illustrated in FIG. 4 may be achieved. Moreover, in this case, the oxidizing power of the second reactant can be enhanced, and at step D, the SiN layer having SiCl termination formed on the wafer 200 at step C can be oxidized to form a silicon oxide layer (SiO layer), which is a layer containing Si and O, on the wafer 200. In this case, a SiO film having a predetermined thickness can be formed on the wafer 200 by performing the aforementioned cycle a predetermined number of times. In addition, the oxidizing power of the second reactant can be increased even when an O₃ gas, an H₂ gas+O₂ gas, an H₂ gas+O₃ gas, or the like is used as the second reactant, and at step D, the SiO layer can be formed on the wafer 200. A SiO film having a predetermined thickness can be formed on the wafer 200 by performing the aforementioned cycle a predetermined number of times.

Furthermore, for example, as illustrated in the following film-forming sequence example, a SiN layer is formed by implementing a set which non-simultaneously performs steps B and C a predetermined number of times (n₁ times, where n₁ is an integer of 1 or more), and thereafter, a SiON layer is formed by oxidizing the SiN layer by performing step D, and this is defined as one cycle and a SiON film may be formed on the wafer 200 by performing this cycle a predetermined number of times (n₂ times, where n₂ is an integer of 1 or more). Even in this case, the same effects as those of the film-forming sequence illustrated in FIG. 4 may be achieved. In addition, in this case, by controlling the aforementioned set number (n₁), it is possible to enhance the controllability of control of N concentration and Si concentration to O concentration in the SiON film as formed, i.e., control of composition ratio of the SiON film.

NH₃→P→[(NH₃→P→SiCl₄→P)×n ₁→O₂→P]×n ₂⇒SiON

NH₃→[(NH₃→P→SiCl₄→P)×n ₁→O₂→P]×n ₂⇒SiON

Furthermore, step A is particularly effective when the state of an underlayer (wafer surface) on which a film is formed is in a state in which a film is difficult to be formed, but step A may be omitted depending on a surface state of the wafer.

For example, as illustrated in the following film-forming sequence example, a SiON film having a predetermined thickness may be formed on the wafer 200 by implementing a cycle which non-simultaneously performs steps B, C, and D, without performing step A, a predetermined number of times (n times, where n is an integer of 1 or more). Even in this case, the same effects as those of the film-forming sequence illustrated in FIG. 4 may be achieved.

(NH₃→P→SiCl₄→P→O₂→P)×n⇒SiON

Furthermore, for example, as illustrated in the following film-forming sequence example, a SiN layer is formed by implementing a set which non-simultaneously performs steps B and C a predetermined number of times (n₁ times, where n₁ is an integer of 1 or more), and thereafter, a SiON layer is formed by oxidizing the SiN layer by performing step D, and this is defined as one cycle and a SiON film may be formed on the wafer 200 by performing this cycle a predetermined number of times (n₂ times, where n₂ is an integer greater than or equal to 1). Even in this case, the same effects as those of the film-forming sequence illustrated in FIG. 4 may be achieved. In addition, in this case, by controlling the aforementioned set number (n₁), it is possible to enhance the controllability of control of N concentration and Si concentration to O concentration in the SiON film as formed, i.e., control of composition ratio of SiON film.

[(NH₃→P→SiCl₄→P)×n ₁→O₂→P]×n ₂⇒SiON

Recipes used in substrate processing may be prepared individually according to the processing contents and may be stored in the memory device 121 c via a telecommunication line or an external memory device 123. Moreover, at the start of substrate processing, the CPU 121 a may properly select an appropriate recipe from the recipes stored in the memory device 121 c according to the processing contents. Thus, it is possible for a single substrate processing apparatus to form films of different kinds, composition ratios, qualities and thicknesses with enhanced reproducibility. In addition, it is possible to reduce an operator's burden and to quickly start the substrate processing while avoiding an operation error.

The recipes mentioned above are not limited to newly-prepared ones but may be prepared by, for example, modifying the existing recipes already installed in the substrate processing apparatus. When modifying the recipes, the modified recipes may be installed in the substrate processing apparatus via a telecommunication line or a recording medium storing the recipes. In addition, the existing recipes already installed in the substrate processing apparatus may be directly modified by operating the input/output device 122 of the existing substrate processing apparatus.

In the aforementioned embodiments, there has been described an example in which films are formed using a batch-type substrate processing apparatus capable of processing a plurality of substrates at a time. The present disclosure is not limited to the aforementioned embodiments but may be appropriately applied to, e.g., a case where films are formed using a single-wafer-type substrate processing apparatus capable of processing a single substrate or several substrates at a time. In addition, in the aforementioned embodiments, there have been described examples in which films are formed using the substrate processing apparatus provided with a hot-wall-type process furnace. The present disclosure is not limited to the aforementioned embodiments but may be appropriately applied to a case where films are formed using a substrate processing apparatus provided with a cold-wall-type process furnace.

In the case of using these substrate processing apparatuses, a film-forming process may be performed by the processing procedures and processing conditions similar to those of the embodiments and modifications described above. Effects similar to those of the embodiments and modifications described above may be achieved.

The embodiments, modifications and the like described above may be appropriately combined with one another. The processing procedures and processing conditions at this time may be similar to, for example, the processing procedures and processing conditions of the aforementioned embodiment.

EXAMPLES First Example

In example 1, a SiON film was formed on a wafer using the substrate processing apparatus illustrated in FIG. 1 and by the film-forming sequence illustrated in FIG. 4 . As the wafer, a bare wafer in which no pattern is formed on its surface, and a pattern wafer in which a pattern is formed on its surface and which has a surface area 23 times the surface area of the bare wafer were used. The processing conditions at each step were set to predetermined conditions which fall within the processing condition range in the aforementioned embodiments.

In a comparative example, after performing step A of the film-forming sequence illustrated in FIG. 4 to form NH termination on the wafer using the substrate processing apparatus illustrated in FIG. 1 , a cycle is performed a predetermined number of times, the cycle including non-simultaneously performing a step B′ of supplying an HCDS gas to the wafer, a step C′ of supplying an NH₃ gas to the wafer, and a step D′ of supplying an O₂ gas to the wafer, whereby a SiON film was formed on the wafer. As the wafer, the aforementioned bare wafer and the aforementioned pattern wafer were used. The processing conditions at steps A, B′, C′ and D′ were similar to the processing conditions of steps A to D of the example, respectively.

Then, the in-plane film thickness uniformities of the SiON film formed in the example and the comparative example were measured. The measurement results are shown in FIG. 8 . The vertical axis in FIG. 8 indicates an in-plane film thickness uniformity (%) of the SiON film. When the value of the in-plane film thickness uniformity (%) is 0, it means that the thickness of the SiON film is uniform from the central portion to the outer peripheral portion of the wafer. When the value of the in-plane film thickness uniformity (%) is larger than 0, it means that the thickness of the SiON film has a distribution which is the largest in the central portion of the wafer surface and is gradually decreased toward the outer peripheral portion thereof, i.e., a central convex distribution. When the value of the in-plane film thickness uniformity (%) is smaller than 0, it means that the thickness of the SiON film has a distribution which is the largest in the outer peripheral portion of the wafer surface and is gradually decreased toward the central portion thereof, i.e., a central concave distribution. In addition, the value of the in-plane film thickness uniformity (%) indicates that the in-plane film thickness uniformity of the SiON film formed on the wafer is better as it approaches zero. The horizontal axis in FIG. 8 indicates a case where a bare wafer is used as the wafer and a case where a pattern wafer is used as the wafer. In FIG. 8 , a white columnar graph indicates a comparative example, and a shaded columnar graph indicates an example.

According to FIG. 8 , it can be seen that the in-plane film thickness uniformity of the SiON film in the example is better than the in-plane film thickness uniformity of the SiON film in the comparative example in any of the case where the bare wafer is used as the wafer and the case where the pattern wafer is used as the wafer. In contrast, it can be seen that the in-plane film thickness uniformity of the SiON film in the comparative example shows a strong central convex distribution when the bare wafer is used as the wafer and a strong central concave distribution when the pattern wafer is used as the wafer. That is, it is understood that the influence of the surface area of the wafer on the in-plane film thickness uniformity can be suppressed such that the influence is lower in the SiON film in the example than in the SiON film in the comparative example. In other words, it is understood that the film-forming method in the example can suppress the so-called loading effect (substrate surface area dependency) such that it is lower than in the film-forming method in the comparative example.

Example 2

In this example, a SiON film or the like was formed on a wafer using the substrate processing apparatus illustrated in FIG. 1 and by the film-forming sequence illustrated in FIG. 4 . At that time, samples 1 to 5 such as a plurality of SiON films having different composition ratios were produced by changing the processing conditions (oxidizing gas supply conditions) at step D. Then, atomic concentrations of Si, N, and O of each film of samples 1 to 5 were measured by X-ray photoelectron spectroscopy (XPS). Furthermore, a wet etching rate (WER) when etching each film of samples 1 to 5 using a hydrogen fluoride aqueous solution (DHF solution) diluted to 1% was measured. FIG. 9A is a diagram illustrating a composition ratio of Si, N, and O in each film of samples 1 to 5 measured by XPS. In FIG. 9A, the vertical axis indicates an atomic concentration (Atomic %) of each element, and the horizontal axis indicates samples 1 to 5. FIG. 9B is a diagram illustrating a WER of each film of samples 1 to 5. In FIG. 9B, the vertical axis indicates a WER (A/min), and the horizontal axis indicates samples 1 to 5.

The processing conditions (oxidizing gas supply conditions) at step D when producing samples 1 to 5 are as follows. An O₂ gas supply flow rate: 0 slm and a supply time of an O₂ gas: 0 second mean that step D was not performed. Other processing conditions were set to predetermined conditions which fall within the processing condition range of the aforementioned embodiments.

(Sample 1)

-   -   O₂ gas supply flow rate: 0 slm     -   Supply time of O₂ gas: 0 seconds

(Sample 2)

-   -   O₂ gas supply flow rate: 3 to 5 slm     -   Supply time of O₂ gas: 10 to 15 seconds     -   Processing pressure: 500 to 1,000 Pa

(Sample 3)

-   -   O₂ gas supply flow rate: 3 to 5 slm     -   Supply time of O₂ gas: 100 to 120 seconds     -   Processing pressure: 500 to 1,000 Pa

(Sample 4)

-   -   O₂ gas supply flow rate: 3 to 5 slm     -   Supply time of O₂ gas: 100 to 120 seconds     -   Processing pressure: 2,000 to 3,000 Pa

(Sample 5)

-   -   H₂ gas supply flow rate: 0.5 to 2 slm     -   Supply time of O₂ gas: 3 to 5 slm     -   Supply time of H₂ gas+O₂ gas: 20 to 30 seconds     -   Processing pressure: 50 to 200 Pa

As illustrated in FIG. 9A, in sample 1 which is a reference sample, although step D was not performed, it was confirmed that an O component is contained in a film. This is considered to be because the surface of the film is oxidized by exposing the film to the atmosphere after film formation. Furthermore, as illustrated in the measurement results of sample 2 and sample 3 in FIG. 9A, it was confirmed that the composition ratio of O in the SiON film formed on the wafer can be increased and the composition ratio of N can be lowered by prolonging the processing time at step D. In addition, as illustrated in the measurement results of sample 3 and sample 4 in FIG. 9A, it was confirmed that the composition ratio of O in the SiON film formed on the wafer can be further increased and the composition ratio of N can be further lowered by increasing the processing pressure at step D. Moreover, as illustrated in the measurement result of sample 5 in FIG. 9A, it was confirmed that, although the processing time is set shorter than that of samples 3 and 4 and the processing pressure is set lower than that of samples 2 to 4 by supplying an H₂ gas+O₂ gas instead of supplying the O₂ gas at step D, the composition ratio of O in the film formed on the wafer can be further increased and the composition ratio of N can be further lowered (composition ratio of N can be set to zero). In addition, it was confirmed that sample 5 becomes a SiO film rather than a SiON film. That is, it was confirmed that the composition ratio of O and N in the SiON film can be controlled by controlling the oxidizing gas supply conditions such as the processing time, the processing pressure, and the gas type at step D.

Furthermore, as illustrated in FIG. 9B, it was confirmed that the lower the composition ratio of O in the film is and the higher the composition ratio of N is, the smaller the WER is (the higher HF resistance is). Further, the higher the composition ratio of O in the film is and the lower the composition ratio of N is, the larger the WER is (the lower the HF resistance is). That is, it was confirmed that the composition ratio of O and N in the SiON film can be controlled by controlling the oxidizing gas supply conditions at step D, whereby the processing resistance (HF resistance) of the film can be controlled.

According to the present disclosure in some embodiments, it is possible to improve film thickness uniformity of a SiON film or a SiO film formed on a substrate in the plane of the substrate.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures. 

What is claimed is:
 1. A method of processing a substrate, comprising: forming a film containing Si, O, and N or a film containing Si and O on a surface of the substrate by performing a cycle a predetermined number of times, the cycle including: (a) forming NH termination on an outermost surface of the substrate by supplying a first reactant containing N and H to the substrate; (b) forming a Si- and N-containing layer having Cl termination by supplying SiCl4 to the substrate to cause the NH termination formed on the outermost surface of the substrate to react with the SiCl4; and (c) causing the Si- and N-containing layer to react with a second reactant containing O by supplying the second reactant to the substrate, wherein (b) is performed under a condition in which Si—N bonds are formed by bonding of Si constituting the SiCl₄ and N constituting the NH termination formed on the outermost surface of the substrate, and at least a portion of Si—Cl bonds which are not converted into the Si—N bonds among Si—Cl bonds contained in the SiCl₄ are held.
 2. The method according to claim 1, wherein (b) is performed under a condition in which the SiCl₄ is not pyrolyzed.
 3. The method according to claim 1, wherein (b) is performed under a condition in which the SiCl₄ is not gas-phase decomposed.
 4. The method according to claim 1, wherein (b) is performed under a condition in which no gas-phase reaction occurs.
 5. The method according to claim 1, wherein (b) is performed under a condition in which SiCl₄ does not generate an intermediate in gas phase.
 6. The method according to claim 1, wherein (b) is performed under a condition in which an adsorptive substitution reaction occurs between the NH termination formed on the outermost surface of the substrate and the SiCl₄.
 7. The method according to claim 1, wherein (b) is performed under a condition in which the reaction of the NH termination and the SiCl₄ is self-limited.
 8. The method according to claim 1, wherein (b) is performed under a condition in which at least a portion of Si—Cl bonds in the SiCl₄ and at least a portion of N—H bonds in the NH termination formed on the outermost surface of the substrate are broken, and Si—N bonds are formed by bonding of Si after at least the portion of the Si—Cl bonds in the SiCl₄ are broken and N after at least the portion of the N—H bonds in the NH termination formed on the outermost surface of the substrate are broken, and at that time, at least a portion of Si—Cl bonds which are not converted into the Si—N bonds among the Si—Cl bonds in the SiCl₄ are held.
 9. The method according to claim 1, wherein (b) is performed under a condition in which Si constituting the SiCl₄ is bonded to N constituting the NH termination formed on the outermost surface of the substrate in a state in which Cl is bonded to each of three bonding hands among four bonding hands of Si constituting the SiCl₄.
 10. The method according to claim 1, wherein (b) is performed under a condition in which Si after at least a portion of Si—Cl bonds in the SiCl₄ are broken is bonded to N after at least a portion of N—H bonds in the NH termination formed on the outermost surface of the substrate are broken in a state in which Cl is bonded to each of three bonding hands among four bonding hands of Si constituting the SiCl₄.
 11. The method according to claim 1, wherein a supply time of the SiCl₄ in (b) is set longer than a supply time of the first reactant in (a).
 12. The method according to claim 1, further comprising (d) supplying the first reactant to the substrate before performing the cycle the predetermined number of times.
 13. The method according to claim 11, wherein a supply time of the first reactant in (d) is set longer than the supply time of the first reactant in (a).
 14. The method according to claim 11, wherein a supply time of the first reactant in (d) is set longer than the supply time of the SiCl₄ in (b).
 15. The method according to claim 1, wherein a supply time of the SiCl₄ in (b) is set such that an amount of an adsorptive substitution reaction occurring between the NH termination formed on the outermost surface of the substrate and the SiCl₄ in a central portion of the substrate becomes substantially equal to an amount of an adsorptive substitution reaction occurring between the NH termination formed on the outermost surface of the substrate and the SiCl₄ in an outer peripheral portion of the substrate.
 16. The method according to claim 1, wherein a supply time of the SiCl₄ in (b) is set such that a thickness of the Si- and N-containing layer formed in a central portion of the substrate becomes substantially equal to a thickness of the Si- and N-containing layer formed in an outer peripheral portion of the substrate.
 17. The method according to claim 1, wherein in (a), the first reactant is supplied to the substrate from a side of the substrate, wherein, in (b), the SiCl₄ is supplied to the substrate from the side of the substrate, and wherein, in (c), the second reactant is supplied to the substrate from the side of the substrate.
 18. A method of manufacturing a semiconductor device comprising the method of claim
 1. 19. A substrate processing apparatus, comprising: a first reactant supply system configured to supply a first reactant containing N and H to a substrate; a SiCl₄ supply system configured to supply SiCl₄ as a precursor to the substrate; a second reactant supply system configured to supply a second reactant containing O to the substrate; a heater configured to heat the substrate; and a controller configured to be capable of controlling the first reactant supply system, the SiCl₄ supply system, the second reactant supply system, and the heater to perform a process comprising: forming a film containing Si, O, and N or a film containing Si and O on a surface of the substrate by performing a cycle a predetermined number of times, the cycle including: (a) forming NH termination on an outermost surface of the substrate by supplying the first reactant to the substrate; (b) forming a Si- and N-containing layer having Cl termination by supplying the SiCl₄ to the substrate to cause the NH termination formed on the outermost surface of the substrate to react with the SiCl₄; and (c) causing the Si- and N-containing layer to react with the second reactant by supplying the second reactant to the substrate, wherein (b) is performed under a condition in which Si—N bonds are formed by bonding of Si constituting the SiCl₄ and N constituting the NH termination formed on the outermost surface of the substrate, and at least a portion of Si—Cl bonds which are not converted into the Si—N bonds among Si—Cl bonds contained in the SiCl₄ are held.
 20. A non-transitory computer-readable recording medium storing a program that causes, by a computer, a substrate processing apparatus to perform a process comprising: forming a film containing Si, O, and N or a film containing Si and O on a surface of a substrate by performing a cycle a predetermined number of times, the cycle including: (a) forming NH termination on an outermost surface of the substrate by supplying a first reactant containing N and H to the substrate; (b) forming a Si- and N-containing layer having Cl termination by supplying SiCl₄ to the substrate to cause the NH termination formed on the outermost surface of the substrate to react with the SiCl₄; and (c) causing the Si- and N-containing layer to react with a second reactant containing O by supplying the second reactant to the substrate, wherein (b) is performed under a condition in which Si—N bonds are formed by bonding of Si constituting the SiCl₄ and N constituting the NH termination formed on the outermost surface of the substrate, and at least a portion of Si—Cl bonds which are not converted into the Si—N bonds among Si—Cl bonds contained in the SiCl₄ are held.
 21. The method according to claim 1, wherein (b) is performed under a condition in which at least the portion of Si—Cl bonds which are not converted into the Si—N bonds are held without being broken. 